Another thing with the display resolution - should I set it to default 1080p or 4K? If I set it to 4096x2160p, the refresh rate automatically gets set to 24 - is this right behavior? My TV is 4K UHD OLED with HDR, FYI. Can it actually play 10-bit HDR material?
Why do you setup 4096? Your TV has only 3840 pixel. Setup this and everything will be OK. HDR works.